Identification documents may be used to verify aspects of a person's personal identity. If issued in the form of a small, mostly standard-sized card, it is usually called an identity card (ID or ID card). Countries which do not have formal identity documents may require identity verification using informal documents.
In the absence of a formal identity document, driving licenses may be accepted in many countries for identity verification. Some countries do not accept driving licenses for identification, often because in those countries they do not expire as documents and can be old or easily forged. Most countries accept passports as a form of identification.
Identification documents may also be used to verify an individual's membership in a group. For example, student identification cards are used as proof that the individual is a student, faculty, or staff at a school. Military identification cards are used as proof that the individual is a member of the armed services.